I am also shopping for a sit down, and recommend that you try them all yourself. I thought I knew what was the "best" for me, but having tried several brands, I've actually ruled out some of the most popular because I didn't enjoy quilting with them. Either the sound of the machine or the vibration or some other aspect caused me to tense up rather than relax.
I was quite surprised by this and it send me back to the drawing board. I have 2 machines left to try, the Innova and the Gammill Charm, but I was quite surprised to find that the machine I had ruled out initially -because of other people's comments- the Janome/Tin Lizzie Artistic 18 in the forward-facing orientation, was the most enjoyable machine for me by far. I tried it expecting not to like it, and it turned out that I didn't want to stop quilting to let the next show attendee have a go at it.
So try them all out for yourself. It's (hopefully) going to be a long relationship and you're going to want it to start with "THIS is the one for ME!"
Michelle